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Re: Elevated Bridge B/C

Posted: May 31st, 2010, 12:09 pm
by ichaelm
How do you get sheets that size that weigh less than all these intricate little bridges made of 1/8 squared or less....

Then again the bridge is practically just one side...
yeah, only 4.50 grams! :o
On another note, anyone notice these pictures of the 1st place B division bridge?

It's completely different than all the others! Or, at least, it looks that way.
I saw that bridge, it look so strange. Does anyone know the construction behind it? Or it's efficiency?
2734 :o

Re: Elevated Bridge B/C

Posted: May 31st, 2010, 12:14 pm
by new horizon
did you/your team build that?
if so, props, because that's amazing.

I'm not a bridge person, but where are the bracings? I can't find any... How can something that simple hold so much weight..?

Re: Elevated Bridge B/C

Posted: May 31st, 2010, 12:22 pm
by Littleboy
Simple=perfect
If something is simple it usually works better than a weird crazy design

Re: Elevated Bridge B/C

Posted: May 31st, 2010, 12:26 pm
by ichaelm
lol no i didnt build it. I just found it on the wiki. Yeah I don't do bridges either :lol: but I find them interesting because I love physics. I have no idea why this is better than all the others though. I guess it's just... strong.

Re: Elevated Bridge B/C

Posted: May 31st, 2010, 12:40 pm
by AlphaTauri
Too bad there's no one we can ask...it's from one of the NC teams (Arendell Parrot) and I don't think there are many people on here who are from NC.

If I had to venture a guess as to why this bridge won, I'd say it's because it's so simple. Less pieces = less chance of spontaneous failure. Also, it doesn't look like it'd be easy to tip over either, with the legs slanting outwards, so that's something else this bridge has going for it. I have no idea how they made it so light, though. 4.50 grams...are you sure there wasn't an antigravity field or something canceling out some of its weight? :lol:

Re: Elevated Bridge B/C

Posted: May 31st, 2010, 7:07 pm
by lllazar
Too bad there's no one we can ask...it's from one of the NC teams (Arendell Parrot) and I don't think there are many people on here who are from NC.

If I had to venture a guess as to why this bridge won, I'd say it's because it's so simple. Less pieces = less chance of spontaneous failure. Also, it doesn't look like it'd be easy to tip over either, with the legs slanting outwards, so that's something else this bridge has going for it. I have no idea how they made it so light, though. 4.50 grams...are you sure there wasn't an antigravity field or something canceling out some of its weight? :lol:
Man, must be some really light balsa....however, the uhh "style?" of the legs is actually really smart, after all triangles are the strongest structural shapes...props to the team, but 4.5 grams is pretty insane :o

Re: Elevated Bridge B/C

Posted: June 1st, 2010, 4:27 am
by eta150
There's clearly a LOT of surface area for the glue, which is great, but there are no tensions members (unless the bottom of the top beam acts as tension). I wonder how it held that much.
EDIT: Actually, I analyzed it, and I think the shape of the top beam (it slants up towards the loading block, the bottom is flat), shows that it acts as tension and compression.

Re: Elevated Bridge B/C

Posted: June 1st, 2010, 5:13 am
by lllazar
There's clearly a LOT of surface area for the glue, which is great, but there are no tensions members (unless the bottom of the top beam acts as tension). I wonder how it held that much.
EDIT: Actually, I analyzed it, and I think the shape of the top beam (it slants up towards the loading block, the bottom is flat), shows that it acts as tension and compression.
Man i wish the kids who made this were on the forum :(

I think it held somewhere in the 12.3-12.4kg range...it was extremely light, 4.5 grams...

Re: Elevated Bridge B/C

Posted: June 2nd, 2010, 12:32 pm
by Balsa Man
Re: the new scoring approach being discussed:
Thanks Bob and Jeff for the good insights on the thinking behind it.
I'm sure lots of folk have opinions on how the rules could/should work. But, for S.O. to work, somebody has to come up a workable set of rules for a lot of different.....made-up events.

In anything competitive, the rules are the rules. The name of the game is to figure out how to win within the rules. That takes understanding of the rules, and the variables in your control - how they do and don't fit within the rules, and the effect of changing them on how you score.

Re: the winning B-Div bridge
Its actually a very good example of what I'm talking about in terms of figuring out how to win within a set of rules.
My hat's off to whoever set off on the path to that design. I suspect a coach (which is fine; that's part of good coaching). If a student did, my hat's really off to them.
Whoever did, they did something really right; backing off, letting go of pre-conceived notions of "how its done"/"how it has been done", looking with fresh eyes at what needed to be done, and educated eyes at what has been done structurally, in bridges and anything else. The broader your knowledge, the more you have to draw from. Applying old ideas/knowledge new ways to new situations-that's exactly where most scientific and engineering breakthroughs come from.
I kick myself for not having done that better myself. There is an interesting analogy from racing. Up until the early 1960s, chassis frames were built using steel tubing. To get good suspension control, the frame needed to be stiff- not bending under cornering/braking/accelerating loads. In a race car, you want it as light as possible. In 1962, Colin Chapman (who founded Lotus) came out with a revolutionary design in the Lotus 25 (a Formula One car). He used aluminum sheet, riveted into .....boxes- the strength of the sheet(in 2 dimensions), and the strength of the shape, in the 3rd dimension, formed a structure much lighter and much stronger than the old tube frame - a "monocoque chassis." Stressed skin and monocoque construction existed in aircraft design going back into the 1930s. It rapidly became 'the way to do it." When carbon fiber came along, it replaced aluminum.

So, well done. Time to think outside the box about towers- what's going on structurally in a top-loaded structure with a defined height, and base. Hmmmm....

Re: Elevated Bridge B/C

Posted: June 26th, 2010, 6:03 pm
by blue cobra
Balsa Man, will we be seeing any pictures of your kids' bridge from this last season? I'm still dying to see it :D